This may be the same site that Daniel found. It is a pitch only device.

I once made a circuit like this one to blink LEDs on a desk plaque. I soldered a board together but did not clean the off the solder flux. The LEDs blinked in an astable pattern that would also fuzz out the TV (I couldn't afford cable in those days). when I cleaned the board it ran fine (unfortunately) and blinked at about 4 Hz.